Re: [RFC PATCHv2 1/2] Export SoC info through sysfs

[Greg KH <greg@kroah.com>]

On Fri, Apr 08, 2011 at 01:19:10AM +0200, Arnd Bergmann wrote:
> On Friday 08 April 2011, Ryan Mallon wrote:
> >>>>> /sys/devices/soc/${NAME}/
> >>>>> /sys/devices/platform/soc${NUMBER}/
> >>>>
> >>>> I prefer the second format here since the path is always the same which
> >>>> makes it easier to write parsing tools. The name should be an entry in
> >>>> the directory rather than the name of the directory itself.
> 
> In the first case, we would ensure that every directory under /sys/devices/soc
> is an SOC device, so you would not need to parse the name at all, which is
> even simpler. I'm open to other arguments either way, but I think this
> one is not particularly important.

I think your proposal is best.

> > > That would mean two separate instances of Linux, just like two systems.  
> > > SMP across multiple SOCs doesn't make much sense, and I don't think they 
> > > are likely to be designed for that ability either.
> > 
> > So we probably don't need the ability to have multiple SoC directories
> > under sysfs then?
> 
> There are systems that have multiple ones, they are just not as common.
> 
> > For the other part of the question, do you think it makes sense for the
> > CPU's to be child devices of the SoC (and for the CPU devices to be
> > potentially symlinked from the SoC directory)?
> 
> No, the CPUs are children of /sys/devices/system, and we should not change
> that. Symlinks sound like a good idea though.

Symlinks are a requirement as multiple cpus can be attached to a single
SoC.

What about multiple cpus that are attached to multiple SoCs?  Why even
try to describe this relationship, what would userspace get out of this
information?

thanks,

greg k-h